(1) Field of the Invention
The present invention relates to the general technical field of safety systems for aircraft, and in particular for aircraft of the rotorcraft kind, e.g. helicopters.
More particularly, the present invention relates to an emergency buoyancy system and to its control method.
(2) Description of Related Art
Such an emergency buoyancy system is a system that enables the passengers and crew of an aircraft to escape in the event of ditching at sea. All aircraft that need to perform missions of transporting people over areas of sea are fitted with such a system. The system should advantageously keep the aircraft afloat for a duration of at least about five minutes.
An emergency buoyancy system includes leak tight compartments and floats that are inflated either under the control of the pilot and/or the copilot, or else under the control of automatic triggering, in particular by using an immersion detector.
On-board present aircraft, the emergency buoyancy system is triggered only in the event of contacting or impacting water. The buoyancy system must have been primed beforehand using a control button when overflying sea and while advancing at a speed of less than 90 kilometers per hour (km/h). An indicator on the pushbutton lights up when the system is primed, to indicate that the system is operational. So long as the system is not primed, an erroneous manipulation on the control stick therefore cannot trigger inflation of the float.
Pressing on the pushbutton indicator or on a pushbutton on the handle of the control stick makes it possible to trigger inflation of the floats manually.
If the crew is not in a position to actuate the buoyancy system manually, inflation of the floats is triggering automatically by the immersion detector.
Document WO 2008/054401 discloses a system serving to inflate anticrash airbags, taking account of the attitude of the aircraft and of the aircraft approaching the ground at an excessive speed.
Document U.S. Pat. No. 7,156,033 B2 discloses a buoyancy system associated with inhibitor means. The inhibitor means are activated in particular when the aircraft is flying above a certain altitude.
Known emergency buoyancy systems nevertheless present drawbacks. The immersion detectors that are used operate in a manner that can be found to be unsatisfactory in certain situations. This applies in particular when an aircraft of the helicopter type turns over. When the helicopter falls off a deck or a platform at sea, the emergency buoyancy system may fail to trigger, e.g. as a result of slipping progressively and in the absence of any violent impacts against the water or in the absence of the aircraft being fully immersed. The nature of the immersion detector, e.g. based on the orientation of gravity, may also give rise to failures to detect immersion, in the event of the helicopter being upside-down.
Furthermore, undesirable untimely inflation of the floats may occur in flight, e.g. as a result of impacts or of a high level of humidity.